The Great Wall of China is a series of fortifications made of stone, brick, tamped earth, wood, and other materials, generally built along an east-to-west line across the historical northern borders of China to protect the Chinese states and empires against the raids and invasions of the various nomadic groups of the Eurasian Steppe. Several walls were being built as early as the 7th century bce; these, later joined together and made bigger and stronger, are now collectively referred to as the Great Wall.
Here one can only see a portion of the great wall. Last survey of 2012 revealed that the wall’s length is 13,170 miles (21,196 km)and is among seven wonders of the world. In general, tourist visiting the Great Wall do not exceed one mile in their exploration, my opinion.